Sharmilee Nyenhuis MD

How Climate Change is Making Your Patients' Allergies Worse

As climate change intensifies, it is not just the environment that suffers—seasonal

are getting worse, too. Global warming has led to increased droughts, wildfires, intense storms, heat waves, and rising sea levels, factors that can contribute to allergies and asthma.

According to the American Public Health Association, the 3 main causes of allergy include ambient air pollution, mold, and pollen.

 The organization also reported that 30% of adults and 40% of children experience nasal allergies.

Featuring Scott Commins, MD, PhD (top left), Sharmilee Nyenhuis, MD (bottom left), Mahboobeh Mahdavinia, MD, PhD (top right), and Kent Lam, MD (bottom right)

Credit: UNC School of Medicine, UChicago Medicine, McGovern Medical School, Macon & Joan Brock Virginia

2025 American Academy of Allergy, Asthma, & Immunology (AAAAI) 

spoke with several experts on climate change’s impact on allergies, exploring strategies clinicians can adopt to mitigate worsening allergic conditions.

, from the University of Texas Health Houston

 from Eastern Virginia Medical School at Old Dominion University

Extended Pollen Seasons and Increased Allergen Potency

Nyenhuis emphasized that pollen seasons are lengthening, especially in the western and southwestern United States, where freeze days have increased by nearly 20.

 This prolonged exposure intensifies symptoms and raises the risk of new allergies. She also noted that air pollution, particularly diesel particles, can amplify pollen’s allergenicity, worsening allergic reactions.

To help patients, Nyenhuis recommended indoor air filtration, wearing masks outdoors, and using hyper-local pollen data instead of historical weather app forecasts, which are becoming less reliable due to climate change.

Air Pollution’s Role in Allergy Development

Mahdavinia explained that air pollutants disrupt the respiratory tract’s epithelial barriers, leading to inflammation and microbiome imbalances in the nose and lungs.

 This can eliminate beneficial bacteria, allowing harmful microbes to thrive and increasing allergy risks. Mahdavinia called for expanded pollen monitoring and broader allergen testing as plant distributions shift.

Climate Change and Emerging Food Allergies

Commins discussed pollen food syndrome, in which pollen absorbed through the skin triggers food allergies.

 He also warned about the rising prevalence of alpha-gal syndrome, a meat allergy caused by tick bites. Warmer winters have expanded tick populations, increasing cases in the US, Europe, Australia, and Asia.

As climate change drives new allergy risks, clinicians must stay alert for evolving conditions such as pollen food syndrome and alpha-gal syndrome. Experts stress the importance of refining allergy diagnostics, improving access to immunotherapy, and implementing preventive strategies to protect patients in an increasingly allergenic environment.

Relevant disclosures include GlaxoSmithKline for Nyenhuis, GENZYME CORPORATION, Optinose US, Inc, and Blueprint Medicines Corporation for Mahdavinia, Regeneron Healthcare Solutions, Genetech USA, and AstraZeneca Pharmaceuticals for Commins, and Optinose US, AERIN MEDICAL, GENZYME CORPORATION, Medtronic, GlaxoSmithKline, Regeneron Pharmaceuticals, and AstraZeneca Pharmaceuticals for Lam.

. chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://www.apha.org/-/media/files/pdf/topics/climate/asthma_allergies.pdf. Accessed March 20, 2025.

Derman, C. Adapting Allergy Care Due to Increased Pollen Seasons, with Sharmilee Nyenhuis, MD. HCPLive. March 1, 2025. 

https://www.hcplive.com/view/adapting-allergy-care-due-increased-pollen-seasons-sharmilee-nyenhuis-md

Derman, C. How Air Pollutants Contribute to Allergies, with Mahboobeh Mahdavinia, MD, PhD. HCPLive. March 1, 2025. 

https://www.hcplive.com/view/how-air-pollutants-contribute-to-allergies-with-mahboobeh-mahdavinia-md-phd

Derman, C. Climate Change’s Impact on Allergies, with Scott Commins, MD, PhD. HCPLive. March 2, 2025. 

https://www.hcplive.com/view/climate-change-s-impact-on-allergies-scott-commins-md-phd

Articles

Climate change worsens allergies by lengthening pollen seasons, increasing air pollution, and driving new food allergies. Experts offer strategies for clinicians.

How Climate Change is Making Allergies Worse—And What Clinicians Can Do

Adapting Allergy Care Due to Increased Pollen Seasons, with Sharmilee Nyenhuis MD

Climate change has recently extended pollen seasons, ultimately affecting 

“[The pollen seasons] expanded much longer than they did previously, and it's affected different parts of the United States more than others,” Sharmilee Nyenhuis, MD, from the University of Chicago, told 

2025 American Academy of Allergy, Asthma, & Immunology (AAAAI)

 in San Diego on her team’s session, “Allied Health: An Overview of Allergic Rhinitis and the Impact of Climate Change on Allergies.” “The west coast and the Southwest seen almost a 20-day increase in freeze days, so again, that lengthens the pollens.”

Nyenhuis added how air pollution also impacts the pollen allergen level, with diesel particles making the pollen more allergenic.

“With that, we are seeing in patients with allergic rhinitis that they have symptoms for a longer period of time and sometimes even more severe symptoms,” Nyenhuis said.

Nyenhuis shared ways to improve rhinitis allergic symptoms within the home, which includes air filtration by using bathroom and kitchen fans. Outside, people can wear a regular surgical mask if they are worried about pollen and an N95 mask for air pollution.

Patients with allergic rhinitis can opt for subcutaneous or sublingual immunotherapy, and Nyenhuis said they are both efficacious treatments. However, she chooses which immunotherapy type to give each patient based on several factors.

If people have multiple allergies, Nyenhus recommends subcutaneous therapy since it only requires about 1 – 3 shots, depending on the number of allergens, and it is taken weekly not daily. This can be helpful if patients have concerns about adherence. However, the US Food and Drug Administration (FDA) has only approved subcutaneous therapy for the allergens of grass pollen, ragweed pollen, and dust mites.

If the patient is allergic to something else, Nyenhuis recommends sublingual immunotherapy.

Overall, Nyenhuis said it is important for allergists to be aware of the lengthening pollen seasons. At the meeting, she also presented the importance of collecting hyper-local pollen data, rather than relying on weather apps that report pollen forecasts but use historical data.

“As things are changing, we might not be able to rely on that historical data as much, so some of the things to do is seeing if there is somebody who's actually doing the Pollen counting…and that data is collected from pollen counters and where people are actually measuring the pollen and then counting the pollen,” Nyenhuis said.

Accurate pollen counts can inform patients whether they should take precautions before leaving their houses. For instance, if they are allergic to grass pollen, and it is a high grass pollen day, they could wear a mask outdoors.

“I think a lot of it is awareness of what are the actual levels of pollen,” Nyenhuis said. “But also thinking about air quality as well and trying to get as much as possible this hyper-local data, because that'll be more representative of what you're experiencing… living in a large city, some areas may be more affected by pollen levels [than] others.”

Relevant disclosure for Nyenhuis includes GlaxoSmithKline.

Nyenhuis, S, Gregory, K, Strong, B. Allied Health: An Overview of Allergic Rhinitis and the Impact of Climate Change on Allergies. Session presented at AAAAI 2025 in San Diego on February 28.

Climate change has extended pollen seasons, particularly affecting the western and southwestern United States, leading to prolonged and sometimes more severe allergic rhinitis symptoms. Air pollution exacerbates pollen allergenicity, with diesel particles increasing allergenic potential. Effective management strategies include air filtration, mask usage, and immunotherapy. Subcutaneous immunotherapy is recommended for multiple allergies, while sublingual is suggested for other allergens. Accurate, hyper-local pollen data is crucial for allergists and patients to make informed decisions. Awareness of pollen levels and air quality is essential for effective allergy management.

HCPLive spoke with Nyenhuis at AAAAI 2025 about ways to help patients with allergies despite the growing pollen seasons.